Method of manufacturing of rectifier elements



Dec. 28, 1948. A. J. MILLER ETAL. 2,457,169

METHOD OF MANUFACTURING OF RECTIFIER ELEMENTS Filed March 12, 1945 2 Sheets-Sheet 1 5100mm fiB/L/TY mm a j ELEC 7WOF0/PMl/Y6 {9" RATE 3e FUME 3250/75/57 TREAT "so 260 2'50 560 so 400 4'50 5'00 550 Mac FDRWAPD CONDl/C- 'T/ V! TY SECOND H647 TRENT/VENT THIRD HEflT TRENT/WENT I50 260 use 360 350 460 450 500 550 056.6.

INVENTORS mm; J. M/LLER .fl uus w. FLE/SHER Dec. 28, 1948. A. 'J. MILLER ETAL 2,457,169

METHOD OF MANUFACTURING OF RECTIFIER ELEMENTS Filed March 12, 1945 2 Sheets-Sheet 2 Patented Dec. 28, 1948 UNITED STATE METHOD OF MANUFACTURING F K'...B.ECTIFIER ELEMENTS Arthur J. Miller, Oak Ridge, Tenn, and Julius W. Fleisher, New York, N. Y., assignors to Federal Telephone and Radio Corporation, New York,

N. Y., a corporation of Delaware Application March 12, 1945, Serial No. 582.278

the elements manufactured according to previ- V ously used methods. a .In the manufacture of selenium elements .in

well known manner a coating of selenium-is provided on a base plate and the selenium layer is annealed by heat treatment to crystallize the selenium. This annealing process is ordinarily done in two heat treatment steps: the first step involves heating the selenium to 120 C. under pressure for about one-half hour; and the second step involves heating without pressure for several hours at a higher temperature just under the melting point of selenium, for example, about 214 C. A treatment is then usually given the selenium with selenium dioxide vapor or selenium vapor after which a conducting counter-electrode is sprayed over the selenium surface.

It has been found that the final treatment .of the selenium with selenium vapor is preferable to the treatment with selenium dioxide vapor since the first mentioned treatment provides a better blocking layer than the later mentioned one. In many cases, however, the a blocking layer thus achieved was still not yet satisfactory and according to the method of the present invention it is possible to provide a still more improved blocking layer.

It is, therefore, the main object to provide a method for manufacturing of selenium elements which have a better blocking layer and electroforming rate than achieved before by using known methods. i

It is a further object of the present invention to provide a method for manufacturing of selenium elements which have a better forward conductivity though the blocking and electroforming rate are improved.

It is still another object of the present invention to provide a selenium element which has improved blocking layer characteristics, electroforming rate and forward conductivity.

With these and otheroblects in view which will become apparent in the following description, the invention will be clearly understood in connection with the enclosed drawings, in which:

Figure '1 shows a diagram of heat treatment temperature against blocking ability and electroforming rate;

Fig. 2 shows a diagram of heat treatment temperature against forward conductivity; and

. 5 Claims. (Cl. Hit-$66).

It has been found that by providing a third,

heat treatment, instead of selenium vapor treatment or selenium dioxide vapor treatment, at a temperature between 300 to 450 C. for two or three seconds, an improved blocking layer compared with that achieved before by the selenium vapor treatment is provided. iv

In Figure 1 it is clearly shown that the lowest blocking ability and electroforming rate is achieved when the manufacturing process is stopped after the second heat treatment of the selenium. If a selenium dioxide vapor treatment is used the blocking layer is quite improved, yet the best results achieved heretofore were obtained by the selenium vapor treatment. The curve shown in Figure 1 in full lines discloses clearly that by providing a third heat treatment Within the temperature range of 300 to 450 C. a

still better blocking layer can be achieved than conductivity is achieved when the manufacturing process is stopped after the second heat treatment. If the second heat treatment is followed by selenium dioxide treatment the forward conductivity is lowered" tremendously. Quite an improvement can be achieved by providing a. selenium vapor treatment instead of a selenium dioxide vapor treatment, yet, as Fig. 2 shows clearly again, the forward conductivity receives still a set back compared with that prevailing after the second heat treatment.

It has been found that the provision of the above described third heat treatment particularly in the temperature range of 300 to 450 C.also improves the forward conductivity compared with that achieved by selenium vapor treatment and is substantially equal to the forward con-' ductivity prevailing after the second heat treatment.

Fig. 3 shows. by example only, anapparatus which can'be used to perform the method according to the present invention. It is emphasized, however, that the apparatus per se as shown cannot be considered as limitation of the present invention. As shown in Fig. 3 a plurality of base finally through another oven '5,'to be exposed to the third heat treatment. The oven 5 is heated up for example by sheeting solid and pipes (not shown) can be inserted into the oven chamber.

Y to introduce when the performance in a C02 atmosphere is preferred. a i

From the above stated findings can be concluded that the substitution of the selenium (lion ide vapor treatment or of the selenium vapor treatment by a third heattreatment particularly in the above mentioned temperature range not ,oniy improves the blocking ability and electroiormine rate of the selenium element but at the same time improves the forward conductivity,.

thus resulting in an improvement of several char= ncteristics oi the selenium rectifier e ement.

It hasbeen further found that m re beneficial results are achieved when the third heat treatmerit takes, place in a C02 atmosphere.

By using the method according to the present invention it is possible to eliminate all the turning and handling by placing a thin strip heater above prising applying the said third heat treatment for a period of two or three seconds in a CO: atmosphere.

t. A selenium rectifier element comprising a base plate having a selenium layer, said layer having been exposed to a first heat treatment at about 120 C. under pressure. a second heat treatment without pressure at a higher temperature I then that applied in the first heat treatment yet below the. meltingpoint of selenium and a momentary third heat treatment, the third heat treatment being at a temperature range between 900 and ate 0.." the selenium layer being cooled between the first and'second heat treatments and between the second and third heat treatments.

5. A selenium rectifier element comprising a base plate having a selenium layer, said layer the conveyorto third heat treat the discs after applying a second heat treatment without pres-' sure at a higher temperature than that applied in the first heat treatment yet below the melting point of the selenium, and after cooling the selesnd appended nium to about room temperature applying e. mo-

mentary third heat treatment at a temperature ranginirom 300 to 450 C. v

2. The method of manufacturing a selenium rectifier element, as set forth in claim 1, the said third heat treatment being applied for two or three seconds. I

8. The method as set forth in claim 1, comhaving been exposed to a first heat treatment at about 0., under pressure, a second heat treatment without pressure at a higher temperature than that applied'in the first heat treatment yet below the melting point of selenium and a momentary third heat treatment, the-third heat treatment being at a temperature range between 300 and 450 C. in a C02 atmosphere, the selenium layer being cooled between the first and second heat treatments and between the second and thir heat treatments.

REFERENCEQ CITED The ,iollowins references ills of this patent:

'iis STA PATENTS Number v Name Date 1,7d3,160 Presser Jan. 14, 1930 2,193,610 Wilson Mar. 12, 1M0 2,215,999 Brunke Sept. 2%, 1940 .1 2,226,718 Geisler Dec. 31, 1940 2,270,187 Thompson Apr. '1, 1942 2,856,094 Saslaw -s Aug; 15, 1944 2,383,555 Baslaw Nov. 28, 1944 2,395,259 mils et al Feb. 19, 1946 are of recordin the 

